Can EGR cause P0300?
A bad EGR valve may cause random engine misfires if it is causing a vacuum leak in the engine. This can cause a vacuum leak in the intake manifold that can cause an intermittent engine misfire. If you run an engine diagnostic, you may see error codes such as P0300, P0100, P0101, P0102 or P0104.
What sensors cause misfires?
If an oxygen sensor or mass airflow sensor is failing, it could give incorrect data to your engine’s computer, causing the misfire. When a vacuum line is broken, it can cause a fuel-injected motor to misfire.